1. Field of the Invention
The invention relates to a luminescent indicator with LED used as a light source and a vehicle rearview mirror apparatus and, particularly, to a luminescent indicator and a vehicle rearview mirror apparatus that allow an improved visibility while offering reduced power consumption, long operating life and low-profiled body.
2. Description of the Related Art
In recent years, LED's (light emitting diodes) are applied to various apparatuses because they have a long operating life and reduced power consumption as compared to conventional bulbs. Since a luminescent indicator using LED has a small light-source size, it is frequently used as a light source for a unit that is subject to a limitation on its dimension.
On the other hand, the power consumption in various electronic devices is apt to increase due to enhancement in its performance and function. A certain ratio of people owns a plurality of television sets or personal computers at home. Further, as communication lines are sped up, the number of certain personal computers that have full-time access to the communication line increases. Therefore, although power consumption in a device itself is reduced, the total power consumption in using multiple devices simultaneously will be not negligible. Especially in lighting devices such as lamps, an increase in power consumption is significant.
Further, in view of environmental protection on global warming or air pollution, electric vehicles that use a motor as drive mechanism without discharging warming gas or hybrid cars that use a combination of motor and small engine are developed in place of vehicles that have a drive mechanism to use fossil fuel such as gasoline. However, even in such new vehicles, it is still important to reduce the power consumption of lighting devices so as to secure a longer cruising distance.
Vehicles such as automobiles and motorcycles are equipped with a rearview mirror apparatus that allows its driver to look backward circumstances. For example, in case of automobile, rearview mirror apparatuses are disposed on both sides of its front window or engine hood while projecting from the car width. Although the rearview mirror apparatus is attached projecting from the car width, it is not easy for a driver of oncoming car or a pedestrian to notice it in the night since it is relatively small. Therefore, a driver of oncoming car, pedestrian or bicycle rider may have a minor collision with the rearview mirror apparatus. Especially, a black rearview mirror apparatus must produce a worse visibility even when the body color is white or so.
Japanese patent application laid-open No.2000-25519 (herein referred to as “prior art 1”) discloses a rearview mirror apparatus with a light (herein called a rearview mirror light) to indicate the projecting of rearview mirror apparatus to prevent the collision accident (ibid., FIGS. 1 and 3).
FIG. 1 is a cross sectional view showing the rearview mirror apparatus 100 disclosed in prior art 1. The rearview mirror apparatus 100 is attached to a door 200 on the right side of a car. The rearview mirror apparatus 100 is composed of: a housing body 101 that is attached to the door 200 and has an opening on the back side; a mirror 102 that is housed in the housing body 101 to close the opening; a support 103 that is disposed behind the mirror 102 to rotatably support the mirror 102 and fixed to the housing body 101; a L-shaped support board 104 that is disposed inside a front face 110a of the housing body 101; and bulbs 105a, 105b, 105c and 105d (composing the rearview mirror light) that are disposed at predetermined intervals on the support board 104.
The support 103 is connected through a semispherical member 103a to the back of mirror 102 and is fixed to the housing body 101. By pushing a desired part of the mirror 102, the mirror 102 can be adjusted to have a desired angle (backward viewable angle) while being rotated around the support 103.
The housing body 10 is made by molding transparent resin and its outer surface is coated with transparent paint that has the same color as the body when light is transmitted therethrough. The housing body 101 has an inner surface 101b with diamond-facets to diffuse radiated light.
The bulbs 105a to 105d are laterally disposed on the support board 104 to illuminate the front face 101a and side face 101c of housing body 101, Electric power is supplied to the bulbs 105a to 105d in conjunction with turn-on of small lamp. The number of bulbs may be arbitrarily varied although the four bulbs 105a to 105d are exemplified.
In operation, light radiated from the bulbs 105a to 105c is shed on the diffusion diamond-facets formed on the inner surface 101b of housing body 101, diffused there, then transmitted through the paint-coated layer on the housing body 101, radiated from the front face 111a to provide forward radiation light 106. Light radiated from the bulb 105d is shed on the side face 101c of housing body 101, then transmitted through the housing body 101 to provide lateral radiation light 107.
Thus, the rearview mirror light radiates the forward radiation light 106 and lateral radiation light 107, thereby allowing an oncoming car driver, pedestrian, bicycle rider, motorcycle rider or following car driver who is on the forward, side or backward to notice the rearview mirror apparatus 100. Thereby, the collision accident with the rearview mirror apparatus 100 can be prevented effectively.
However, the rearview mirror apparatus of prior art 1 has problems as described below.
(i) Since many bulbs are needed to illuminate the front face and side face of housing body, the power consumption must be increased to cause an increase in battery load.
(ii) Since the bulbs are attached to the support board through sockets, its depth is difficult to reduce. Thus, it is not easy for the rearview mirror apparatus to be low-profiled.
The above problems may be solved by using LED with reduced power consumption instead of bulb.
However, even when LED's as many as bulbs are provided, there occurs unevenness in light intensity in the entire lighting range of rearview mirror light since LED has a light intensity lower than bulb. Instead, when the number of LED's is increased to prevent the unevenness, the reduction effect of power consumption by using LED must be spoiled.
Japanese patent application laid-open No.2000-307807 (herein referred to as “prior art 2”) discloses a linear light source unit that light emitted from LED is entered into a light-guiding member and then externally radiated being reflected on a groove provided on the light-guiding member. Its object is to offer a wider lighting even when using one LED.
In the linear light source unit, of light emitted from LED, light component to be, to the right and left side, separated by parabolic surface heads to the longitudinal direction of light-guiding member, being repeatedly subjected to total reflection at the second side surface and first side surface of light-guiding member. During the reflection, light entered to the first side surface with an incident angle smaller than its critical angle θ c is externally radiated. In this case, most of light to be irradiated to the surface of groove is reflected being diffused radially. Most of light to be emitted from LED and entered into the intermediate interface passes through the hole while being refracted at the interface, being entered into a plastic material again from the upper interface, then being radiated from the center of the first side surface of light-guiding member.
However, the linear light source unit of prior art 2 has the following problem. Since light is entered from the intermediate interface through the hole into a plastic material again, there occurs unevenness in light distribution since the external radiation property of light lowers when a factor, e.g. stain, to block the transmission of light exists in the hole.